


The Recessive Gene

by Everyday_Im_Preaching



Category: Captain America (Movies), Marvel Cinematic Universe, The Avengers (Marvel Movies)
Genre: Adult Breastfeeding, Alpha!Steve, Alpha/Beta/Omega Dynamics, Alpha/Omega, Established Relationship, Lactation Kink, M/M, Male Lactation, Pregnancy, Pregnancy Test, Unplanned Pregnancy, omega!Tony
Language: English
Status: Completed
Published: 2018-05-22
Updated: 2018-05-22
Packaged: 2019-05-10 07:21:45
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,457
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14732468
Author URL: https://archiveofourown.org/users/Everyday_Im_Preaching/pseuds/Everyday_Im_Preaching
Summary: Tony is delighted after Steve returns from an impromptu doctor's appointment-- turns out that he has a very rare, recessive gene that causes him to lactate whenever he's around a pregnant omega--typically his mate.Oh, wait.





	The Recessive Gene

**Author's Note:**

> Hi guys! I've finally written something for this ship! You'd think I'd write more for Marvel, since I literally watch every movie that comes out. Bleh. 
> 
> If you enjoy this fic, and would like to see more, please leave a comment below! I'd love to hear your opinions.

>  

“So, what’d the doctor say, big guy?” Tony asked; Steve had left a note for him that morning, being the old, sentimental man, he was, telling Tony that he was heading to the doctors for an impromptu appointment. When Tony had asked _why,_ Steve had told him that everything was fine and not to worry.

But of course, Tony _worried._ What else was he supposed to do when his alpha had to go to the doctor? Go about the day like nothing had happened? He’d told Steve as much, trying not to check his phone more than was necessary—which again, didn’t _happen._ He’d never admit it, but he would mother hen Steve to the moon and back.

There was the rustle of a plastic bag that caught Tony’s attention; he turned his head to see the oddest expression painted over Steve’s face. He was perplexed in a way that Tony didn’t know how to read, and certainly couldn’t smell on him.

“Steve?” Tony asked, voice soft and stern.

“I…uh, well, it didn’t go bad,” Steve replied, rolling his lips between his teeth. “Tony…you aren’t hiding anything from me, are you?” He asked, reaching into the bag at his feet.

Tony’s eyes darted down to the bag, and then up at Steve, trying to catch his eye. “Not that I know of. Nothing incredibly secretive goes on around here anymore—unless you count that one time we were almost caught fucking against the—”

“—Tony, are you…pregnant?” The question interrupted the beginning of Tony’s tangent, catching him off guard. He blinked owlishly at Steve, trying to come up with some sort of answer to that.

“I…you got me, I haven’t a clue how to respond. What are you talking about?” He nervously rolled up his sleeves, feeling oddly like he was on trial. “I mean, I haven’t been on birth control for awhile now, don’t think I can get pregnant at my age. Not with this, either.” He tapped the electromagnet in his chest.

Steve nodded, as if he knew all this information already. “So, I went to the doctors this morning because I woke up, and I…” His throat caught on the words trying to come out of it. “…I woke up, and I was lactating. Well, I didn’t know it was milk, but I did know it wasn’t normal.”

“You were _what_ ?” Tony’s voice didn’t raise in pitch, _no._ He would never admit to that. “You’re kidding me. What day is it? FRIDAY, what day is it? Tell me it isn’t April first.” His words fell flat as Steve pulled out an opened box of nursing pads. “What…wait, what does that have to do with me being pregnant?”

“That’s what I wondered too,” He set the pads on a nearby table, going to unzip and shrug off his jacket. “The doc said that, there’s a…oh, what’s it called? Recessive gene, in some alphas. When their mate, or an omega near them that they consider part of their… _pack_ becomes pregnant, they start to lactate for the pup in question.” Tony stared at spots on Steve’s shirt where he could see the outline of the pads, and a thin bralette to hold them in place. “So, my mind went to you. There aren’t any omegas that hang around this place—actually, there’s Peter, I guess, but he’s a good kid. Too young to even have had his first heat yet.”

Tony was caught between wanting to laugh and wanting to choke up at the idea of Steve— _Steve,_ his _alpha,_ lactating in order to feed a baby. Half of him was delighted. That was the omega half, the half that instantly flickered to life the moment he scented his alpha was in the building. The _other_ half of him, normally sane and rational, was on the verge of _panic._ Unless the doctor was wrong that meant that he was pregnant. Or he was about to have a long talk with Peter about the birds and the bees.

“I guess…I guess that means we need to take a pregnancy test,” Tony suggested, keeping his voice slow and even. “Alright, I’m up for it. See if we can become dads this late in life.”

“You aren’t _that_ old,” Steve told him, coming over with open arms, perfect to snuggle into. Tony flicked his eyes over him, doing his best not to cave into them. “What?”

“How long are you going to be producing breast milk?” Tony asked as he was gathered up in Steve’s arms all the same. Steve pressed a kiss to the top of Tony’s head, pulling him close to his chest. Tony rolled his eyes, letting the alpha rock him to and fro—calming pheromones were spilling out of Steve. Tony didn’t _feel_ like he was that stressed, and he couldn’t smell it on himself, but Steve had always been overprotective either way .

“It depends,” Steve replied.

Tony waited for Steve to finish his sentence, and when he didn’t, he slid his arms up, winding them around his neck and tugging gently. Steve looked down, curious. “You going to finish your sentence, or am I suddenly a mind reader?”

“Who knows, maybe you are?” Steve suggested. “It’s possible it’ll go away in a couple weeks. It’s more likely that it’ll stick around until after you start to produce milk of your own—or maybe even until the pup is weaned.”

“Oh, are we just assuming I’m pregnant then?” Tony murmured, lacing his fingers together. “If I am pregnant, that’s going to be one hell of a miracle.”

Steve let out a short hum, brushing his lips against Tony’s forehead. “I mean, we could always hunt down Peter and ask him—”

“—nope,” Tony answered before Steve could finish his question. “Did you grab one while you were out?” There was a nod of affirmation, followed by another kiss to his brow. “You’re going to have to let me go, you know. As comfortable as I am letting you watch me piss, not as comfortable getting said piss on your shoes.”

Steve unwillingly let him go, lifting a hand and drawing his knuckles down the side of Tony’s cheek. Tony snorted, turning his hand to kiss at them. “You’re a _huge_ sap.”

“The idea of you pregnant is…it’s something that I can’t imagine,” Steve began, and then caught himself. “Wait, no, I could. I _can._ You’d be so beautiful.”

“Just go get me the test, Steve,” Tony grunted, crossing his arms over his chest. “Stop letting that dumb alpha brain of yours get caught up in a fantasy.” He followed Steve over to the plastic bag. “What did I tell you about using plastic bags?”

“That they’re bad for the environment and I should use the reusable ones in the kitchen,” Steve answered, squatting to fish the pregnancy test out of the bag. “I was in a hurry this morning. I didn’t think I’d be dropping by the grocery store.”

Tony plucked the box from his hands, and then leaned over to press a kiss to Steve’s brow. “I get to suck on those later, right?” He asked, getting an amused half-snort. “I’m one-hundred percent serious. I want to.”

“We’ll see what happens.”

 

Tony stood in the bathroom long after the pregnancy test showed up positive. He simply stood there, staring at the elongated piece of plastic, unable to find anything to say. Steve was out in the living room, no doubt pacing back and forth—a pregnancy test didn’t take twenty minutes.

“Are you okay?” Steve was done with waiting, it seemed.

Tony pushed off from the bathroom counter, unsure of whether to be honest. Honesty was the best policy, but it also wasn’t always Tony’s strong suit. “I’m good, just thinking over inflation rates—how much do you think college is going to cost in about eighteen years, give or take nine months?”

The door was opening before Tony could get to it, and he couldn’t help but laugh at Steve’s enthusiasm—he found himself brought, once again, into those unfairly burly arms. Steve pressed his face into Tony’s neck, nuzzling the skin there and running his lips against the mating scar he’d given him years ago.

“Hey, are you scenting me?” Tony asked playfully as Steve rubbed their throats together, a possessive rumble vibrating through him. “Who said you could do that?”

“The pup in your stomach,” Steve responded easily, kissing below Tony’s ear. “I can’t believe you’re _pregnant._ Can I see the test?”

Tony’s lips curled into a soft smile, and he nodded. He pushed Steve away from him and then reached back toward the counter, taking the capped test and flashing it at the alpha. Steve took it in his hands gently, eyes bright with the kind of pride that had Tony beaming in response.

“We’re going to be parents,” He whispered.

“Are you crying? Are you legit tearing up?” Tony asked, bringing his hands up to cup Steve’s face. He wiped at the beginning of tears, trying not to laugh. “It’s okay, it’s alright. Come here big guy.” He brought Steve into a hug, grunting when it was returned, tight and unforgiving. “You’re a good alpha.” He whispered suddenly. “And you’re going to be such a great dad.”

“You’re just buttering me up because you want to mess with my chest,” Steve replied, through it was thick with tears. He was still burying his face in Tony’s neck again all the same, once again scenting him to the best of his ability, considering the angle.

“Damn right I am.”

 

There was a lot to get through. Tony convinced Steve _not_ to immediately call everyone they knew in favour of setting up a doctor’s appointment instead. One short visit later, it was confirmed that _yes,_ Tony was pregnant. And _yes,_ the lactation was directly connected to it.

“Hey, stop being so handsy,” Tony ordered when they got home. Steve wasn’t listening—within seconds, Tony found himself being lifted off the floor and into a careful cradle. “Okay, do you remember that conversation we had early about your alpha brain being dumb? That’s happening again. And I want _down.”_

“There’s no harm in carrying you to the bed,” Steve stated airily, clearly ignoring Tony. Tony rolled his eyes but didn’t fight him on it. “I know the little gears in your mind are turning— _no,_ I haven’t been secretly trying to pup you.”

“I didn’t think it was a _secret._ We knew it might happen, when I stopped taking my birth control,” Tony pointed out; he was temporarily shifted to one hand as Steve opened the door to their shared bedroom. “It was just statistically unlikely.”

Steve shrugged, laying Tony down on the bed. “Well, glad you didn’t become another statistic,” Before Tony could complain, Steve was kissing him, fingers wandering over his sides, pinching the cloth of his shirt between his fingers and dragging it upward.

“Oh no, you get undressed first,” Tony ordered, pushing the hands away. A displeased growl left Steve, but it was soft and unsure. On the verge of _hurt._ “At least the shirt.”

“ _Tony,_ ” Steve tried to sound exasperated, realising what he wanted.

“You’ve just…you’ve just got to let me at them, _please._ I need to,” He reached his hands up, tugging at the collar of Steve’s shirt. “Look, I’ll make you a deal—you let me play with yours now, and when mine are full of milk, you can play with them.”

Steve looked at him for a moment, eyes narrowing. Tony matched Steve’s expression to a ‘T’, chuckling when he sighed. He sat up and tugged his shirt free, and then tossed it off the side of the bed. Nursing pads fell and then were brushed off the bed in a single sweep of Steve’s hand. He proceeded to gesture at his chest, flinching only slightly when cold hands grabbed at them.

Tony sat up, humming in absolute _delight._ He liked to suck on Steve’s nipples during a normal romp in the bed—them being full of milk enhanced his desire to do so. He wiggled closer, feeling his pants rake up under hungry palms. “You aren’t going to regret this.”

“I tend not to,” Steve revealed, shuddering as Tony pinched his nipples between his fingers. Milk dribbled free, wetting Tony’s fingers. “Jesus.”

Taking that as a good sign, Tony dipped his face down and took a single, swollen nipple into his mouth. Steve inhaled sharply, one of his hands darting up to cup the back of Tony’s head. Tony brought his other hand up to knead the other breast, pinching at the nipple and groaning as he milked it with his fingers. Fat droplets of milk slipped out, slicking Tony’s fingers further.

The milk was mild and sweet on Tony’s tongue, the flavour almost addicting as it sparked across it. Steve grunted and laid a hand over the one kneading his breast, squeezing it tightly. The bed bounced slightly—a hot flash of pride ripped through Tony as he realised that Steve was beginning to _hump the bed._

“Taste good?” Steve asked, sounding oddly breathless. Tony nodded, sucking harder, running his tongue over the soaking wet, sensitive skin. “Fuck, Tony. I can’t wait to return the favour.”

Tony pulled free, licking his lips. “I can’t wait either,” He replied, switching to the other nipple, pulling his hand free and taking Steve’s with it. He entwined them, nuzzling at the second, still full breast with a hum. “You’ve got the perfect tits for this, _alpha._ No wonder you started leaking, with pillows like these.” He kissed the edge of Steve’s nipple, getting him to growl. “Perfect for a kid to latch onto.”

The hand on the back of his head _yanked,_ pulling toward the bed. He flailed for a second, breath hitching as he was pinned tight to the bed at the mention of the pup. “Woah, _woah—_ ”

“—I’m going to scent you now,” Steve’s voice was low and hungry. “Bathe you in it.”

“Well, _fuck_ . Go on then,” Tony muttered. He closed his eyes and tilted his head upward, offering his neck. “It’s all yours, Steve. Remind me who seeded me in the first place.” Another growl, _louder_ this time. “Remind me of who’s pup this is.”

The way that Steve twisted his hips and then rolled them forward had Tony clutching him tight, wrapping his arms around his neck and pulling him close. He pressed his lips to Steve’s ear, whispering his next words so only he could hear. “I love you, Steve Rogers.”

A soft laugh escaped Steve, breaking him free from his intent to rut, if only briefly. “I love you too, Tony.”  

**Author's Note:**

> Well hello there!
> 
> Song for this fic:  
> Lie To Me by Mikolas Josef  
>  
> 
> Want to stay updated? Want to chat or shoot me a prompt? Have an idea that you'd like me to consider for this pairing? Feel free to click [here](http://everyday-im-preaching.tumblr.com/) to do all these things and more!


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